The scaling potential of any given water is dependent upon complex chemical and physical interactions of the various constituents dissolved therein. Scaling of water bearing appliances specifically those which employ heat as part of their function typically manifests itself by a hard incrustation comprised primarily of calcium carbonate (CaCO3). This compound is formed by the following chemical reaction:Ca(HCO3)2+heat→CaCO3↓+CO2+H2OIt usually occurs directly on heat transfer surfaces resulting in increased energy consumption, failure of the heating element, or plugging of conduits and orifices. There are many methods known in the art to eliminate or inhibit this reaction. Perhaps the most well known and practiced treatment technique is ion exchange water softening.
The formation of calcium carbonate particles follows a stepwise progression which includes the following elements:                1) Saturation with respect to calcium;        2) A shift in the alkalinity equilibrium to favor the formation of the carbonate ion;        3) Nucleation; and        4) Particle formation        
It is well known in the art that when operated in the hydrogen form, a weak acid cation resin removes cations that are associated with alkalinity. The degree of removal and ultimate working capacity of the media is dependent primarily upon the Hardness:Alkalinity ratio (H/A), flow rate and temperature. Chemically the process can be depicted as follows:
Carbonic Acid readily disassociates to water and carbon dioxide.H2CO3H2O+CO2 
The changes that occur during this process have the effect of reducing the Calcium content of the water, shifting the carbonate, bicarbonate, carbonic acid equilibrium to favor the CO2 species, and lowering the pH. Generally these changes can be quantified in a predictable manner. In order to utilize this information and apply it in the treatment of water a number of “indices” have been developed to predict the tendency of a particular water to form a Calcium Carbonate scale. These have been collectively referred to as Calcium Carbonate Saturation Indices. Among the most popular are: The Langelier Saturation Index (LSI), the Ryzner Stability Index (RSI), the Puckorius Scale Index (PSI), and the Calcium Carbonate Precipitation Potential (CCPD). All are based on determining the equilibrium state of the water in question. In general: Water that is oversaturated with respect to Calcium Carbonate will tend to precipitate CaCO3. Water that is under-saturated with respect to Calcium Carbonate will tend to dissolve CaCO3. Water in equilibrium with Calcium Carbonate will have neither CaCO3 precipitating or dissolving tendencies. These models are far from perfect, however they do provide a means to gauge the effect of changing water chemistry in order to achieve a desired finished water quality. An example of one such index and its significance is shown below:
Langelier Saturation Index (LSI)LSI=pH−pHs
Where:
pH=The measured pH of the water
pHs=The pH at saturation and is defined as:pHs=(9.3+A+B)−(C+D)
Where:
A=(Log10[TMS]−1)/10
B=−13.12×Log10(° C.+273)+34.55
C=Log10[Ca+2 as CaCO3]−0.4
D=Log10[Alkalinity as CaCO3]
Significance
                LSI>0—Water is supersaturated and tends to precipitate a scale layer of CaCO3         LSI=0—Water is in equilibrium with CaCO3; a scale layer of CaCO3 is neither precipitated nor dissolved        LSI<0—Water is under-saturated, tends to dissolve solid CaCO3         
For over 50 years, water softeners have been used in residential and commercial applications to remove or reduce the hardness (dissolved Ca and Mg) in the water. This produced the benefit of eliminating or reducing scale formation in water heaters and appliances, eliminating or reducing soap scum formation which allows for more efficient use of soaps and detergents, thereby simplifying cleaning tasks in the home, in the laundry and in personal grooming. The hardness removal or reduction has been historically provided by water treatment systems that utilized ion exchange technology. U.S. Pat. Nos. 4,337,153 and 5,300,230 describe systems that are typical of many that have been applied to this technology over the years. In general, an ion exchange water softener removes dissolved Calcium and Magnesium ions from the water and exchanges them for equivalent number of Sodium or Potassium ions. Sodium and Potassium ions do not form the same detrimental types of scale and scum as do hardness ions. Once an ion exchange system has removed a predetermined quantity of Calcium and Magnesium, it can no longer remove any more hardness and has reached its capacity. To allow it to continue to remove hardness it must be regenerated by introducing excess sodium or potassium ions to drive off the removed hardness ions. This process produces a discharge waste that includes not only the removed hardness ions but also excess sodium or potassium ions. This discharge also includes the chloride salts of these ions and is generally called a “brine” waste. Using this process, these products have provided home and business owners the benefits of soft water for years, efficiently and effectively.
Predominantly over the last decade, concerns over the brine discharge have begun to develop. These are based on the potential for these discharged brine wastes to eventually end up in our waterways, rivers, lakes etc and also in the discharges from waste water treatment plants. The position held by some is that these brine wastes cause an elevated chloride and or sodium level in either the waterways or the wastewater treatment plant thereby making those waters less desirable for their intended uses such as recycling and/or crop irrigation. These issues have produced legislation that in some parts of the country have outlawed the use of ion exchange water softeners.
One effective means of continuing to provide soft water to a home or business even in these restricted areas is to provide an ion exchange system but to perform the regeneration in another location so that there is no local waste brine discharge. In those cases, the tanks would be removed and taken to a facility where a dedicated waste pipe can take the waste brine discharge to an acceptable location such as the ocean or controlled evaporation ponds etc. While this is possible and is being effectively applied today, the home or business owner is inconvenienced by the necessity of having to open their home or business to service people on a frequent basis and the movement of the somewhat bulky tanks in and out of the home or business is difficult, time consuming, and can cause possible property damage.
Alternatives to sodium or potassium chloride regenerants have been proposed. For example, Kunin et al, U.S. Pat. No. 6,340,712 teaches a solution for the regeneration of a Strong Acid Cation Exchange Resin comprised of potassium acetate, or potassium formate with citric acid and octyl phenol ethoxylate. Similarly, Cole, U.S. Pat. No. 4,298,477 employs an ionizable salt of morpholine. Both of these alternatives do not lend themselves as a comparable substitute for residential or commercial applications in terms of cost, availability or use.
Additionally, many non-ion exchange based systems or devices have been developed. U.S. Pat. Nos. 4,299,700 and 4,235,698 are examples of technologies presented to provide home and business owners with alternatives to ion exchange water softening. The results produced by these and many other such devices are questionable and reports vary widely about their effectiveness. In any case they claim to provide some degree of scale reduction or prevention and at least some degree of other soft water benefits such as use of less soaps, easier household cleaning etc. These alternative systems or devices utilize a wide variety of technologies including magnetic fields, electromagnetic fields, template assisted nano crystal formation, and others. It should also be noted that using industry accepted water testing methods (Standard Methods for the Examination of Water and Wastewater) none of these devices produces a measurable difference in the water chemistry make up after processing.
It has also been known for years that there are alternative ion exchange systems that can remove hardness. U.S. Pat. Nos. 4,235,715; 3,458,438; 3,423,311; 2,807,582, 6,746,609; and 7,632,412 show examples of systems where a weak acid cation (WAC) resin can be used to remove hardness and alkalinity in the water. It should be noted that the application of these types of resins have been predominately industrial in nature, i.e. applicable for high pressure Boiler feed water and Open Recirculating Cooling Tower Systems. Additionally they consist of multiple process steps, are designed for complete hardness removal, employ a decarbonation step, and are designed as a regenerable system. Therefore, a need exists for an efficient, simple and cost effective method of reducing scale in residential and commercial applications.